抄録
fwa is a late flowering epi-mutant in Arabidopsis thaliana. FWA is stably silenced in A. thaliana but in related Arabidopsis species, FWA expression and DNA methylation levels vary in vegetative tissue. In this study, we show that variation in FWA expression in field isolates having identical DNA sequences is associated with changes in DNA methylation and may change over time. Vegetative FWA expression is correlated with decreased methylation at non-CG sites in the region upstream of the transcription start site in species related to A. thaliana and we conclude that methylation of this region is critical for FWA silencing in these species. In A. thaliana, FWA expression is affected by methylation in regions both upstream and downstream of the transcription start site. Ectopic thaliana FWA expression causes a late flowering phenotype, but over-expression of lyrata FWA does not. In A. thaliana, stable silencing of FWA to prevent late flowering may have evolved through the selection of large tandem repeats and spread of the critical methylated region to include these repeats.
